Clinical studies and tests have shown that thoracic duct drainage is a mode of therapy by which the deleterious effects of the cell-mediated immune response in man could be abrogated by removal of thoracic duct lymphoytes.sup.1. Thoracic duct drainage is a technique by which the thoracic duct lymph and its contained lymphocytes are diverted from the body to eliminate one or all of the lymph components. The presumed mechanism is depletion of lymphocytes and possibly depletion of certain immune globulins. In order to produce attenuation, experience has demonstrated that drainage must be continuous for periods of one month or longer. FNT .sup.1 H. K. Johnson et al., Transplantation Proceedings, Volume IX, No. 3 (September), 1977).
Presently the procedure is costly and technically demanding because the lymph must be processed to remove the cells and then re-infused intravenously. Alternatively, the lymph is discarded and replaced by human serum albumin. Cost estimates for a month of treatment are in the order of twenty to fifty thousand dollars. Although donor or cadaver kidney transplantation becomes more expensive with thoracic duct drainage, there is little or no added morbidity or mortality, and improved graft survival rates are generated. If the cost could be reduced and the technique simplified, greatly improved donor and cadaveric transplant results would be assured.
In general the flow rates and the quantity of bodily fluid involved is somewhat variable. One investigator.sup.2 reported on the concept of extra-corporeal lymph dialysis and envisioned flow rates ranging from 1.5 to 2.5 liters per day. However, in four patients the flow rate ranged from 4 to 14 liters per day and averaged in excess of six liters per day. Since no means of bypass was available, it was necessary to collect, dialyze, and infuse the total flow from each patient daily. FNT .sup.2 Serles et al., Transactions of the American Society for Artificial Internal Organs, Volume 11, page 165, 1965.
In addition, fluid pressure must be carefully controlled. Animal studies have shown that clamping the thoracic duct cannula.sup.3 would cause the rapid development of alternate channels which would completely divert all flow from the cannulated duct. Attempts to connect the thoracic duct cannula directly to the venous catheter were only successful when duct pressure exceeded the venous pressure. In fact, since duct pressure varies with metabolic rate, intervals exist when venous pressure substantially exceeds duct pressure. Under these conditions blood could enter the venous catheter and clot. FNT .sup.3 loc. cit.
It appears, therefore, that a device used to drain fluid from a thoracic duct must be one that does not produce any back-pressure favorable to the development of collateral channels or cause the lymphatic valves.sup.4 to become incompetent. On the other hand, if the suction pressure is too great the thoracic duct could be forced to collapse. FNT .sup.4 Goss, Gray's Anatomy, Lea & Felshiger, 29th Ed., 1973, page 735
Moreover, since lymph flow rates can vary anywhere from three to one thousand milliliters per hour, the apparatus used to drain or pump the fluid from the duct must adjust almost instantly to this range of flow rates.
In addition, the apparatus should have several channels or flow paths--one for metering proportionately an anticoagulant such as heparin or preferably trisodium citrate in a saline solution and a second flow path for infusing anti-humoral drugs, for example.
The lymph fluid drawn off by the apparatus would be collected, filtered, treated and/or purified and then redirected back into the patient. The removed lymphocytes would be discarded or used for some other purpose. Another method is phoresis or cytophoresis. Another possibility, under investigation, is to install an extra-corporal bed to which the lymphocytes can attach themselves. In addition, a protein A absorbent may be employed to remove the immune complexes in the lymph. Finally, the drainage procedure provides a ready source of antigen for the production of antilymphocyte serum.
Thus, prolonged lymphodepletion by way of thoracic duct drainage can provide excellent pre-transplant immunosuppression for donor or cadaver kidney recipients. A simple, reliable, easy to control device reducing the constant attention and diligence of medical and nursing personnel would improve the acceptance of this technique and reduce present costs.